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Remove example and experimental

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Signed-off-by: Levi Harrison <git@leviharrison.dev>
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Levi Harrison 2021-09-27 07:00:08 -04:00
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32
docs/querying/operators.md
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@ -44,37 +44,7 @@ the result.
The following trigonometric binary operators, which work in radians, exist in Prometheus:
* `atan2` (based on https://pkg.go.dev/math#Atan2, _This is experimental_)
A usecase of `atan2` is converting directional data between the [polar](https://en.wikipedia.org/wiki/Polar_coordinate_system) (r, theta)
and [cartesian](https://en.wikipedia.org/wiki/Cartesian_coordinate_system) (x, y) coordinate forms.
Example:
Take some wind speed and direction data in the polar form. To get a trend over a
longer period of time, it's not correct to just average out the direction data.
The polar data needs to be converted into the cartesian form:
```
wind:northwards = windspeed * cos(rad(winddirection))
wind:westwards = windspeed * sin(rad(winddirection))
```
Having done that, the longerterm averages over northwards and westwards now make sense:
```
wind:northwards:avg1h = avg_over_time(wind:northwards[1h])
wind:westwards:avg1h = avg_over_time(wind:westwards[1h])
```
The "average" direction can be extracted out of these again by using `atan2`:
```
wind:direction:avg1h = deg(wind:northwards:avg1h atan2 wind:westwards:avg1h)
```
The Wikipedia article on the circular mean has more about this calculation:
https://en.wikipedia.org/wiki/Circular_mean
* `atan2` (based on https://pkg.go.dev/math#Atan2)
Trigonometric operators allow trigonometric functions to be executed on two vectors using
vector matching, which isn't available with normal functions. They act in the same manner